U.S. Pat. No. 4,323,140 (Foscarini et al.) discloses a safety platform for use in a vertical shaft such as a manhole. The platform comprises a pair of support beams with the ends of each support beam mounted in the wall of the shaft. At least one panel extends across the shaft and bridges the support beams with a novel wedge clip at one end of the panel to allow the panel to be opened or secured in the closed position. A novel pivoting means is provided at the other end of the panel which pivotally secures the panel to the opposite support beam. The platform may be installed easily with fewer problems than the prior art yet provides increased safety factors for the user.
U.S. Pat. No. 9,133,629 (Copeland) discloses a safety apparatus adapted for retrofitting vertical enclosures is shown. The safety apparatus may include a support frame, a grate platform, and telescoping support legs adapted to fasten to an enclosure wall. The apparatus may also include a hinged hatch defining an opening configured to allow a person to be pulled through the platform.